**1. Introduction**

122 New Approaches to the Study of Marine Mammals

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**5. References** 

Kerr, PI). This work was supported by EPA GRO Fellowship Assistance Agreement No. MA-91739301-0 (C. Wise, PI), NIEHS grants ES016893 and ES10838 (J. Wise Sr., PI), NOAA grant #NA03NMF4720478 (J. Wise Sr., PI), ARO grant # W911NF-09-1-0296 (J. Wise Sr., PI), the Maine Center for Toxicology and Environmental Health, Ocean Alliance, the Campbell

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For countless generations, civilization had a relative insignificant impact on the marine environment, particularly on marine mammal species. However, with the dawning of the industrial revolution, a dramatic increase in the utilization of marine species (including whales) as a food source and other industrial purposes resulted in a radical reduction in the numbers of some species during the subsequent years, leading to a notable decrease in marine biodiversity during the 20th century. Fortunately, this exploitation was accompanied by increased awareness and campaigns by environmental and ethical lobby groups, resulting in more controlled and managed whaling activities, which in turn lead to markedly improved whale numbers [1]. However, the tide shifted once again with the dawning of the new millennium, characterized by ever growing industrial development and rapid human population growth. As a result, natural resources came under increased pressure and in particular, development and growth led to the creation of massive amounts of waste and pollutants. Consequently, high levels of marine pollution, especially near urban regions, became a serious threat to the health and well-being of marine mammals, including cetaceans.

The first reports of skin disease in cetaceans date back to the 1950's [2]. However, over the last 60 years the frequency of these reports steadily increased. The question, therefore, arose as to whether scientists are just more aware of this phenomenon and consequently report more cases, or whether the occurrence of these lesions is indeed on the increase. Many natural factors such as ecto-parasites, water temperature and salinity are role players in these diseases. However, anthropogenic impact can no longer be ignored, since these influences can even affect the natural factors by escalating their effect. This brings one to another imperative question; whether these factors are linked, or whether they are merely the result of a coincidence. The aim of this review is therefore, to take a closer look at the

© 2012 Mouton and Botha, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2012 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

skin of cetaceans, the occurrence of skin lesions among these mammals, the microbes that seem to be the causative agents, as well as contributing factors such as anthropogenic activities.

Cutaneous Lesions in Cetaceans: An Indicator of Ecosystem Status? 125

germinativum. The primary function of these keratinocytes, constituting 95% of the epidermis, is to provide a barrier against adverse environmental conditions, such as heat, radiation, water loss and penetration by pathogens. In cetaceans, this barrier is provided by lipokeratinocytes, responsible for the production of both keratin and lipid droplets [12, 13]. These lipids enhance the capability of the lipokeratinocytes to act as physical barrier within a hypertonic environment, and contribute to the unique buoyancy, streamlining, insulation and caloric characteristics of cetacean skin [12]. This physical barrier represents the first line

**Figure 1.** A cross section of cetacean skin, showing the general anatomy of the epidermal, dermal and hypodermal layers (Illustrated according to previous findings [4, 30]; as well as own unpublished data)

The primary role of skin is to provide a physical barrier against the environment and this presents the first line of defence. However, crucial immune components form integral elements of the skin, providing the subsequent layers of defence with increasing specificity. Potential microbial invaders will be confronted by the physical, innate (non-specific), chemical and granulocyte barrier (adaptive or specific immune system) that evolved over time to eradicate these invaders, digest invading cells into smaller antigens, and finally to programme lymphocytes in order to provide long term protection against the particular

**2.2. The Barrier: Second and third lines of defence** 

microbe [13].

of defence against the environment and prospective invaders.
